The gross mortality of patients in the United States with end-stage renal disease (ESRD) treated by hemodialysis (HD) has increased over the past decade. This has occurred despite numerous advances in the technology associated with HD, and compares unfavorably with trends in other developed nations. The goal of this project is to conduct a Pilot Study which will determine the feasibility of implementing a larger multi-center, prospective, randomized trial to assess the effects of different hemodialysis techniques upon morbidity and mortality. At least 50 chronic HD patients stratified for comorbid illnesses from each of 3 centers will be randomized into a 2 (4) factorial study examining the effects of dialysis modality (high efficiency vs high flux), membrane type (cellulosic vs polysulfone) and dialysis prescription (KT/V 0.851.0 vs 1.2-1.4) delivered over 3 or 4 hours time. Because certain patient-related factors such as age, gender, nutritional status, blood pressure (BP) , presence of diabetes mellitus and condition of the HD access, can interact with the treatment-related variables to be tested in the study, a program of high quality medical care will be undertaken in a uniform manner for all subjects entered. The major outcome of this Pilot Study is the determination of the feasibility of conducting a larger study, by the assessment of the ability to achieve recruitment, retention and compliance of subjects; and the assessment of the frequency of the occurrence of clinical events such as the withdrawal for medical reasons or due to adverse effects of the experimental protocols.